1. Field of the Invention
This invention relates to synthetic absorbable devices, and more particularly, to synthetic absorbable filaments comprising extruded and oriented polymers of poly(alkylene oxalates).
2. Description of Prior Art
Absorbable filamentary materials have traditionally been comprised of natural collagenous materials obtained from sheep or beef intestine, commonly known as catgut. More recently, it has been proposed to manufacture synthetic absorbable fibers from polyesters of hydroxycarboxylic acids, notably polylactide, polyglycolide, and copolymers of lactide and glycolide. Such synthetic absorbable products are described in U.S. Pat. Nos. 3,636,956, 3,297,033, and elsewhere in the literature. Polyesters of succinic acid have also been suggested for at least partially bioresorbable surgical articles as disclosed, for example, in U.S. Pat. No. 3,883,901.
The present invention provides for polymers of poly(alkylene oxalate) to be melt extruded into pliable, monofilament fibers having a high level of softness and flexibility and which are absorbable in animal tissue without significant adverse tissue reaction. The fibers have good initial tensile and knot strength and can be sterilized with cobalt-60 without serious loss of these properties. The higher alkylene oxalate polymes have good in vivo strength retention and are absorbed slowly while the lower alkylene oxalate polymers are characterized by rapid absorption.
Polymers of poly(alkylene oxalates) and the preparation thereof are described in the art. Carothers et al, J. Amer. Chem.. Soc. 52, 3292(1930), for example, describes the ester interchange reaction of diols such as ethylene glycol, 1,3-propanediol, or 1,4-butanediol with diethyl oxalate to yield a mixture of monomer, soluble polymer and insoluble polymer. The reaction of oxalic acid and an alkylene glycol to form polyester resins is described in U.S. Pat. No. 2,111,762, while the preparation of polyesters of fiber-forming quality from dicarboxylic acids and diols is described in U.S. Pat. No. 2,952,652. Superpolyesters of fiber-forming quality and derived from dibasic acids plus glycols are described in U.S. Pat. Nos. 2,071,250 and '251. Linear polyesters of oxalic acid have been reported as having high melting points, being soluble in many solvents, capable of forming films, and readily hydrolyzed [Savinov et al, Polymer Science USSR 6, 1475 (1964)].
The absorbability of poly(alkylene oxalate) polymers in animal tissue has not been known prior to the present invention, and there has been no suggestion in the art for the use of poly(alkylene oxalate) polymers in surgical applications. In particular, there has been no suggestion in the art that absorbable fibers having good tensile properties could be prepared from poly(alkylene oxalate) polymers or that such fibers would have any useful application in the fabrication of surgical devices.
It is accordingly an object of the present invention to provide new and useful articles of poly(alkylene oxalate) polymers. A further object of this invention is to provide synthetic absorbable filaments of poly(alkylene oxalate). It is yet a further object of this invention to provide absorbable surgical aids and prostheses fabricated of fibers or cast or machined from blocks of poly(alkylene oxalate) polymers.